David Sullivan and David Gold have completed their takeover of West Ham United, buying 50% of the club with an option to acquire the remaining 50%. They will have operational and commercial control of the club with immediate effect and the duo, who sold Birmingham City to Carson Yeung this season, said Gianfranco Zola will definitely stay on as the club's manager. The deal values West Ham at £105m.

"We will spell out the book we are taking over," Sullivan said on BBC 5 Live. "The imbalance in the squad and the crazy wages the Icelandics were paying that brought the club to its knees."

Sullivan confirmed that Karren Brady, who was managing director at Birmingham, will become vice-chairman at Upton Park. He told Sky Sports that the club was in a "serious mess". "I don't think we would have bought West Ham if we weren't fans. It is a serious mess there but we are West Ham fans and it is nice to see that we beat off two foreign investors.

"Zola is absolutely staying. I can say that categorically. West Ham United need stability after all the recent upheavals. We appointed four managers and parted company with two at Birmingham in 16 years. We believe in our managers and give them the time and support they need," he added, revealing that he wants to take West Ham into the Champions League in the next decade. "We have a seven-year plan to get them into the Champions League.

"We are deeply and passionately involved in West Ham. It is where I have wanted to be for 20 years. We have done [what we have done] in a way that is good for Birmingham and we have got the club we wanted. Over the next seven years we will spend a lot of money."

Sullivan said part of their plan for the future of West Ham is to move from Upton Park to the Olympic Stadium. "It is the natural home for West Ham," he said. "We hope to persuade the government to let us move into the new Olympic Stadium and I believe the people of east London would support that move."

Sullivan and Gold became the favourites to buy the east London club after their rival Tony Fernandes, chief executive of AirAsia and team principal of the new Lotus F1 team, pulled out of the race.

Sullivan added: "West Ham is a bigger club than Birmingham with bigger aspirations and I appreciate that we have to achieve a lot more. It will be an immense privilege to lead this great football club and more importantly its supporters. Our first priority has to be securing the Premier League status of West Ham. I believe the players at this club have shown great commitment in trying circumstances and the new board and I will get behind them in every way we can."